This application is based on applications No. 16637/2000 and 371812/2000 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an apparatus and method for producing an electrophotographic photoreceptor for use in electrophotographic apparatuses such as copiers, printers and the like. Particularly, the invention relates to the apparatus and method for producing electrophotographic photoreceptor wherein a coating solution is applied to an outer periphery of a cylindrical coated member.
2. Description of the Related Art
The electrophotographic apparatuses, such as copiers and printers, have conventionally employed the electrophotographic photoreceptors.
The usual practice heretofore followed in producing the electrophotographic photoreceptor has been to apply to the outer periphery of the coated member a variety of coating solutions including a photosensitive layer coating solution.
Various methods have conventionally been used for applying to the outer periphery of the coated member the various coating solutions including the photosensitive layer solution. It has been a general practice to use a dip coating apparatus such as shown in FIGS. 1(A) and 1(B).
In the dip coating apparatus shown in FIGS. 1(A) and 1(B), a coating solution 2 contained in a tank 1 is introduced by a pump 4 through a feed pipe 4 to a filter 5 so that the filter 5 may remove foreign substances from the coating solution 2. Subsequently, the resultant coating solution 2 is pumped into a dip coating vessel 6 via the feed pipe 4.
A cylindrical coated member 10 is dipped in the coating solution 2 in the dip coating vessel 6 to a predetermined depth while an overflow of the solution 2 from the dip coating vessel 6 is recovered by a solution recovery portion 7. The recovered solution 2 is returned to the tank 1 via a return pipe 8. On the other hand, the coated member 10 thus dipped in the coating solution 2 is withdrawn therefrom at a predetermined rate whereby the coating solution 2 is applied to the outer periphery of the coated member 10 in a predetermined thickness.
Where the coating solution 2 is applied to the outer periphery of the coated member 10 by dipping the coated member 10 in the coating solution 2 in the dip coating vessel 6, the coated member 10 must be sealed at its upper end before dipped into the coating solution in order to prevent the coating solution 2 from adhering to an inner periphery of the coated member 10. Unfortunately, this involves cumbersome operations.
If the rate at which the coated member 10 is dipped in the coating solution 2 is increased, air enters the coating solution 2 to produce air bubbles which will adhere to the outer periphery of the coated member 10, causing thickness nonuniformities in the coated layer. Hence, the productivity is lowered because of the inability to increase the rate at which the coated member 10 is dipped in the coating solution 2.
More recently, a first charge transport layer and a second charge transport layer with various additives added thereto are laid over the outer periphery of the coated member 10 in order to enhance various performances of the electrophotographic photoreceptor.
A process for forming the first and second charge transport layers on the outer periphery of the coated member 10 encounters the following problem if the formation of the first charge transport layer on the outer periphery of the coated member 10 is followed by the application of the coating solution 2 for second charge transport layer to the first charge transport layer, the application done by dipping the coated member 10 in the coating solution 2 for second charge transport layer and then withdrawing therefrom the coated member. That is, a part of the first charge transport layer is caused to run as dissolved by the coating solution for second charge transport layer, disabling the production of the electrophotographic photoreceptor with stable characteristics.
There have, in recent times, been proposed a spray coating process wherein the coating solution is applied to the outer periphery of the coated member by spraying the solution onto the outer periphery thereof, and a ring coating process wherein the coating solution is supplied through a periphery of a guide portion for applying the solution to the outer periphery of the coated member passed through the guide portion, as taught in Japanese Unexamined Patent Publication No.10(1998)-104855.
However, the following problems exist with the spray coating process wherein the coating solution is sprayed onto the outer periphery of the coated member. That is, the loss of coating solution is great. Additionally, air bubbles are prone to enter the solution coated over the outer periphery of the coated member. Besides, it is difficult to lay a uniform coating of the solution over the outer periphery of the coated member.
In the ring coating process wherein the coating solution is supplied through the periphery of the guide portion for applying the solution to the outer periphery of the coated member passed through the guide portion, the absence of the coated member in the guide portion results in spilt coating solution. For this reason, the ring coating process is adapted for continuous introduction of the coated members into the guide portion. However, if the coated members are not introduced into the guide portion in accurate alignment, the outer peripheries of the coated members are differently coated with the solution so that electrophotographic photoreceptors of steady characteristics cannot be obtained.
Furthermore, the spray coating process and ring coating process lay the solution coating on the overall area of the outer periphery of the coated member so that the photosensitive layer is formed on the overall area of the outer periphery of the coated member.
Unfortunately, when a gap between the electrophotographic photoreceptor thus fabricated and a developing roller is adjusted using rollers pressed against opposite ends of the photoreceptor, a cumbersome operation is required for peeling off the layer at opposite ends of the photoreceptor in order to prevent the gap between the photoreceptor and the developing roller from being varied due to gradual wear of the layer at the opposite ends of the photoreceptor.
A first object of the invention is to accomplish a uniform and efficient application of the coating solution to the outer periphery of the cylindrical coated member.
A second object of the invention is to ensure a stable production of electrophotographic photoreceptors of steady characteristics by preventing the dissolution of a previously formed layer on the outer periphery of the coated member when the layer is applied with the coating solution.
The foregoing objects are accomplished in accordance with the invention by providing an apparatus for producing electrophotographic photoreceptor which applies a coating solution to an outer periphery of a cylindrical coated member and comprises: a guide portion permitting passage of the coated member therethrough; a coating-solution feed portion disposed around an outer periphery of the guide portion and allowing the coating solution to flow over an upper end of the guide portion thereby applying the solution to the outer periphery of the coated member; a coating-solution feeding assembly for feeding the coating solution to the coating-solution feed portion; a coating-solution recovery portion disposed around an outer periphery of the coating-solution feed portion via a partitioning wall for recovery of the coating solution flowing from the coating-solution feed portion over the partitioning wall; and an openable communicating portion for communication between the coating-solution feed portion and the coating-solution recovery portion.
Such an apparatus for producing electrophotographic photoreceptor is used to apply the coating solution to the outer periphery of the coated member in the following manner. When the cylindrical coated member is passed through the guide portion, the coating-solution feeding assembly operates to feed the solution to the coating-solution feed portion while the communicating portion for communication between the solution feed portion and the solution recovery portion is closed so that the solution flows from the coating-solution feed portion, around the outer periphery of the guide portion, over the upper end of the guide portion. Such an overflow of the solution over the upper end of the guide portion is applied to the outer periphery of the coated member passed through the guide portion. On the other hand, an excessive coating solution flowing over the partitioning wall is recovered by the coating-solution recovery portion around the outer periphery of the coating-solution feed portion.
When, on the other hand, the coating solution is not applied to the outer periphery of the coated member, the communicating portion is opened to establish the communication between the coating-solution feed portion and the coating-solution recovery portion. With the communicating portion thus opened, the coating solution fed to the coating-solution feed portion by the solution feeding assembly is prevented from flowing over the upper end of the guide portion because the solution in the solution feed portion is introduced into the solution recovery portion via the communicating portion.
These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention.